<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
        width: 100px;
        height: 100px;
        background-color: red;
       }

       #box1{
        margin-bottom: 200px;
        clip-path: circle(50%);
       }

       #box2{
        margin-top: 100px;
       }
    </style>
</head>
<body>
    <div id="box1" class="box"></div>
    <div id="box2" class="box"></div>
</body>
</html>
<!-- 父元素的高度是由子元素撑开的，子元素的高度是由内容撑开的，
    子元素的高度加上子元素的margin-top和margin-bottom就是父元素的高度，    